The present invention relates to new polyfluoro compounds and, more particularly, polyfluoroalcohols of the hemithioacetal type, which form valuable intermediates for the synthesis of polyfluoro derivatives, especially ionic surface-active agents.
In U.S. Pat. No. 3,655,732, which relates, inter alia, to acrylic monomers of general formula: ##STR1## in which R is a halogen atom or a methyl radical, R.sub.F denotes a perfluoralkyl radical and R' and R" denote alkylene bridges, it is indicated (column 4, lines 63-72) that the hemithioacetals of formula: EQU R.sub.F --R'--S--CH.sub.2 OH (II)
are not accessible by the known methods. Since the corresponding acrylic monomers: ##STR2## cannot therefore be obtained by direct esterification, it is proposed in the abovementioned patent to prepare these monomers indirectly by reacting a thiol R.sub.F --R'--SH with formaldehyde and hydrochloric acid to form a chloromethyl derivative R.sub.F --R'--S--CH.sub.2 Cl which is then reacted with sodium acrylate or methyacrylate; the operating conditions are not given. Furthermore, according to the literature (H. Bohme, Chem. Ber. 69, 1610; patent DE 845,511; H. Bohme et al., Ann. 563, 54), the reaction of a thiol with formaldehyde and hydrochloric acid must be carried out at very low temperature (from -15.degree.to -5.degree. C.). It has been found, however, that when it is applied to fluorothiols R.sub.F --R'--SH, this reaction does not yield chloromethyl derivatives, but thioacetals (R.sub.F --R'--S).sub.2 CH.sub.2.